Proposed in vitro studies include an evalaution of endothelial injury using measurements of altered function such as altered permeability, modulated PGI2 synthesis, changes in endothelial cell-derived growth factor synthesis and thrombin membrane recepotr number. These studies will utilize the endothelialized membrane filter technique recently developed here. Proposed experimental animal studies will utilized the baboon model to examined endotoxemia, the effects on drug combinations on cannula platelet consumption and mathematical modeling of 111 Indium-platelet accumulation on woven Dacron graft A-V shunts. In patients we propose to study platelet granular release to measure platelet activation in vivo and to determine the optimal pharmacologic regimen in the prevention of graft accumulation of 111-Indium-platelets.